Australia's largest warship took part in joint drills with the Philippines and the United States in the disputed South China Sea on Monday, as they seek to strengthen defence ties in the face of China's growing military presence.

China deploys hundreds of coast guard, navy and other vessels to patrol and militarise reefs in the contested waters, which it claims almost entirely despite an international ruling that its position has no legal basis.

HMAS Canberra is one of several ships involved in Exercise Alon in the Philippines, which is being held for the first time as part of Australia's annual Indo-Pacific Endeavour activity. Alon is Tagalog for "wave".

More than 2,000 troops from Australia and the Philippines are taking part in the August 14-31 air, sea and land exercises. About 150 US Marines are also participating.

Monday's simulated air assault in the south of the Philippine island of Palawan happened around 200 kilometres (125 miles) from the Spratly Islands, where longstanding tensions between Manila and Beijing have flared.

"Like the Philippines, Australia wants a peaceful, stable and prosperous region which respects sovereignty and which is guided by rules-based order," Hae Kyong Yu, Australia's ambassador to Manila, said at Tarumpitao Point Airfield.

Such exercises were "critical" because "through these we are putting our words into action", she said.

The United States, Japan and Australia will also hold joint naval exercises off the Philippines this week.

"That's always been the plan," Captain Phillipa Hay, commander of the Australian Amphibious Task Force, told reporters on board the HMAS Canberra.

"Those ships have come from Talisman Sabre (exercises in Australia) and everyone is on their way home, it's very normal for us to train in company with partners when we proceed to and from exercises."

The drills come after a Philippine resupply mission to Second Thomas Shoal in the Spratlys was blocked by Chinese Coast Guard vessels using water cannon on August 5, triggering a diplomatic spat and international outrage.

One of the charter boats carrying supplies to the outpost was prevented from reaching the shoal, while the other succeeded in unloading its cargo.

The Philippine military has said it will send more supplies to the remote outpost, where a handful of Filipino marines are stationed on a rusty navy vessel.

The BRP Sierra Madre was deliberately grounded on the reef in 1999 to check China's advance in the waters.

China has demanded the Philippines remove the vessel and defended its actions as "professional".